AP02 - bones and cartilage Flashcards
Name 3 types of cartilage
hyaline
elastic
fibrous
Where is hyaline cartilage roughly found?
lining articular surfaces of synovial joints (other than TMJ)
What is the TMJ and what cartilage does it use?
temporomandicular joint
fibrocartilage
What does cartilage ECm typically have>
collagen
proteoglycans (like aggrecan)
What does the ground substance of hyaline cartilage contain?
What is the function of this substance?
glycosaminoglycans (3 types):
hyaluronic acid
chondroitin sulphate
keratin sulphate
traps water - frictionless
Why is hyaine cartilage particularly strong?
collagen (II)
What cartilage group does articular cartilage belong to?
hyaline cartilage
What are the layers to articular cartilage?
tangenital layer (collagen parallel to bone surface) transitional zone (large chondrocytes) radial layer (cartilage is partially calcified)
How well is cartilage vascularised?
Why is this significant?
not!
dependent on diffusion through hydrated matrix for survival - metabolites originate from the synovial fluid
What two processes dictate cartilage tissue turnover?
anabolism
catabolism
How might cartilage anabolism be affected by stress or disuse?
stress - anabolic activity can’t keep up
disuse - inhibits anabolism, net degeneration
What is the first stage in development of OA?
changes in articular cartilagelimit ability to withstand compressive forces
stressed chondrocyts release tissue breakdown particles
What is the second stage of OA development
necrosed tissue is surrounded by focal clumps of proliferating cartilage
surviving chondrocytes attempt to repair lesion
What is the third stage of OA development
Once the bone is exposed, microfractures of the trabeculae occur
What is the fourth stage of OA development
osteoblasts respond by forming new bone, where other areas become necrosed
degeneration and regeneration cycle limits strength
Give 3 general functions of bone
mechanical support
calcium homeostasis
haematopoiesis
What is periosteum?
2 fibro-collagenous membranes, with osteoblasts (for proliferatio)
Covers the whole bone other than bits with cartilage
What do osteoblasts make, and where?
What else might this structure be called?
osteons, which surround central canals with neurovasculature and osteoblasts
Haversian system
What is the structure of marrow bone?
What happens to marrow bone over time?
spaces with haematopoietic cells (red) or fat (white)
over time, the bone gets more fatty
Cortical bone: location functino periosteum tissue turnover blood supply
diaphysis of long bones structural support thick slow sparse
Cancellous bone: locatin funcion periosteum tissue turnover blood supply
metaphyseal or marrow bone, in tarsals and carpals, diploe of flat bones
metabolic function
thin
rapid
rich
What is the diaphysis?
shaft of long bone, doesn’t cope well with torque
define Epiphysis
growth plate - mitotically dividing cartilage
capable of hypertrophy
define metaphysis
widening aspect between diaphysis and epiphysis
define epicondyle
profection close to the condyle for ligament and tendon attachment
What is woven bone?
irregular bone in developing and growing bones, or in healing fractures
It is remodelled into lamellar bone
What is the structure of an osteon?
osteocytic lacunae occur with canaliculi radiating through the lamellae, facilitating intercellular communication
How does intramembranous ossification occur?
osteoblasts differentiate directly form mesenchyme and begin secreting osteoid - forms flat bones
How does endochondral ossification occur?
pre-existing matric of hyaline caratilage is eroded and invaaded by osteoblasts, which then beigin osteoid production
Define synarthrosis
a rigid cartilaginous join between two bones
Define synostisis
fused bones - immovable
How might collagen fibres be arranged to offer greater stability?
concentric rings, weightbearing along a greater axis
What type of ossification are flat bones formed by?
intramembranous ossification
What happens to chondrocytes over their lifetime?
proliferate away from the blood, so they eventually stop mitosis and grow
they then calcify and die
